U.S. Pat. No. 5,576,106 (Kerbow et al.) discloses a process for grafting an ethylenically unsaturated compound onto the surface of the particles of fluoropolymer powder. The ethylenically unsaturated compound provides polar functionality to the fluoropolymer, which is otherwise non-polar. The utility of the resultant grafted fluoropolymer powder is disclosed to be to act as an adhesive to adhere dissimilar materials together, such as tetrafluoroethylene/ethylene (ETFE) copolymer to polyamide. To demonstrate the interaction between the grafted powder and the polyamide, a blend of grafted powder and polyamide is made by simple mixing of these components in a weight ratio of 67:33 (55:45 by volume), and the resultant blend is compression molded to yield plaques which exhibit improved tensile elongation.
European Patent Application Publication EP 0 761 757 discloses a fluorine-containing polymer alloy of a grafted fluorine-containing polymer and a polymer containing no fluorine, the fluorine-containing polymer having hydrogen atoms bonded to carbon atoms of its main chain. The grafting is done by melt mixing a fluorine-containing polymer having hydrogen atoms bonded to main-chain carbon atoms, a grafting compound having a linking group and a functional group, and a radical-forming agent (peroxide), apparently either simultaneously with or prior to mixing with the polymer containing no fluorine to form the alloy. No amount of grafting compound actually grafted to the fluorine-containing polymer is disclosed, and the average particle size of the dispersed fluoropolymer is relatively large, i.e., 0.7 .mu.m (700 nm) and larger. In attempts to evaluate this grafting technology, the maximum amount of maleic anhydride that could actually be grafted to ETFE fluoropolymer was no more than 0.2 wt %. The color of the product indicated residual decomposition products from the grafting chemistry, and no bond of such grafted fluorine-containing polymer to 6,6-polyamide was obtained in coextrusion.
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